Spherical-aberration-free observation of profile images of the Au(011) surface by defocus-modulation image processing

Abstract

Spherical-aberration-free profile images of a reconstructed Au(011) surface have been successfully observed by a high-resolution transmission electron microscope combined with defocus-modulation image processing. In the processed images, both surface shape and lattice image were seen more clearly than in the original images, demonstrating the high potential of the processing for determining atom positions. Some of the intensity peaks observed at the topmost layer of the 2 × 1 missing-row reconstructed surface have shifted in ∾0.02 nm toward the surface as predicted by LEED experiments, but one of them has been displaced outward ∾0.05 nm. Using through-focus images calculated by a dynamical electron diffraction theory and an image formation theory, computer simulations of the image processing were performed. By comparison with the simulated results, the displacements of the lattice image are confirmed to be due not to the effect of remaining spherical aberration or an artifact of processing but to the displacement of atoms in the crystal.